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CHAPEL HILL, N.C. — Sexual activity is a fact of life for many teenagers, according to research. However, a new vaccine could prevent some of the greater risks that sexually active teenagers face.

Data from the Centers for Disease Control and Prevention show 10 percent to 20 percent of incoming high school freshmen have had sex, while 30 percent to 60 percent of seniors are sexually active.

The teenagers are at risk for sexually transmitted diseases, and the human pappillomavirus, or HPV, can be caught without sexual intercourse, experts said.

"In fact, it does not require sex to transmit it, just close contact," said UNC epidemiologist Dr. David Weber. "Rubbing up against each other, even digital manipulation with the fingers, can transmit these viruses."

Weber said even condoms don't offer complete protection from HPV. However, there's now a new vaccine called Gardasil, which contains four of the close to 100 strains of HPV: two that protect against venereal warts and two that prevent cervical cancer.

"Even though it's only a small number of strains, in fact, those two types prevent against 70 percent of cervical cancer and more than 90 percent of venereal warts," said Weber.

The vaccine must be given before infection. It is licensed for young girls and women between ages 9 and 26, with a special emphasis on immunizing adolescent girls between 9 and 13.

The immunization can be grouped with other vaccines now recommended for adolescents, including the TDAP vaccine that protects against tetanus, diptheria and whooping cough. Adolescents are also advised to be vaccinated for meningitis.

The HPV vaccine is given in three separate doses, months apart. The total cost for the vaccine is around $350, but insurance typically offers coverage. The vaccine has been shown to offer up to 95 percent effective protection against the human papillomavirus.